Graphics Reference
In-Depth Information
and have it light things up like the real
sky, there is a drawback. Hemi lamps do
not cast shadows. So, an outdoor scene
lit with only a hemi lamp appears flat and
completely unrealistic, like
Figure 5.8
.
For that reason, hemi lamps are inade-
quate for the main lighting in a scene.
However, this does not mean that hemi
lamps are useless. For example, in an
outdoor scene with a strong sun lamp,
extra illumination can be added by using
a downward-facing light-blue hemi lamp
and an upward-facing green hemi lamp.
The blue is for the sky, while the green
gives objects a downward tint as though
light were reflecting off the green grass.
When using hemi lamps like this, start
your Energy settings very low: in the
0.1-0.3 range.
Hemi lamps are good for providing a
baseline, directional illumination to scenes.
Area Lamp
Figure 5.9
shows an area lamp and its
controls. Clearly, there is a little more
going on here. Area lamps have a Distance control, which means that their location affects the scene (unlike
hemi or sun lamps). Unlike the point lamp, the direction that an area lamp is pointing is important. They
only cast light in the way they are oriented.
Figure 5.6
Shadows from a sun lamp are parallel. Those from other types
diverge.
Area lamps have two controls on the
Area Shape
panel, one a toggle between square and rectangular,
the other a size control. Unlike every other lamp type, area lamps have a physical size. This is because
they are used to represent light that emanates from an entire area, like a window or a large ceiling fixture.
You can see the visualization of the area lamp's size in the 3D view portion of
Figure 5.9
. When set
to
Square
, a single value controls its size. Used as a
Rectangle
, you can adjust height and width inde-
pendently. Feedback in the 3D view is immediate, so you really don't need to worry which of the rect-
angle's axes is which when your lamp is rotated at an odd angle. It will be obvious as you adjust the
controls.
Area lamps with Ray Shadow enabled can provide some of the most realistic shadowing effects available
within Blender's renderer. While the standard ray shadows that are available to the other lamps produce
hard-edged shadows, altering the
Samples
value in the Shadow panel for area lamps can produce excel-
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